Claus P. Gebhardt

Wave observation in the marginal ice zone with the TerraSAR-X satellite

This article investigates the penetration of ocean waves into the marginal ice zone (MIZ), observed by satellite, and likewise provides a basis for the future cross-validation of respective models. To this end, synthetic aperture radar images from the TerraSAR-X satellite (TS-X) and numerical simulations of the European Centre for Medium-Range Weather Forecasts (ECMWF) are used. The focus is an event of swell waves, developed during a storm passage in the Atlantic, penetrating deeply into the MIZ off the coast of Eastern Greenland in February 2013. The TS-X scene which is the basis for this investigation extends from the ice-free open ocean to solid ice. The variation of the peak wavelength is analysed and potential sources of variability are discussed. We find an increase in wavelength which is consistent with the spatial dispersion of deep water waves, even within the ice-covered region.

The Potential of TerraSAR-X to Observe Wind Wave Interaction at the Ice Edge

This paper performs a study on sea state and wind fields at the ice edge boundary by utilizing information from different sources including synthetic aperture radar (SAR) satellite imagery, weather and sea state analyses from the European Centre for Medium-Range Weather Forecasts, shipborne in-situ measurements, and AMSR2 ice charts. The basis is a Stripmap scene from the TerraSAR-X satellite acquired on October 18, 2015, at

Overview of the Arctic Sea State and Boundary Layer Physics Program

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High resolution wind and wave measurements from TerraSAR-X and Tandem-X satellites in comparison to marine forecast

18 UTC, in support of the cruise of the research vessel R/V Sikuliaq in the Beaufort/Chukchi Sea. This scene covers an area with a length of more than 100 km and comprises both the marginal ice zone and, for the largest part, open water. The wave and wind field is retrieved from satellite at high spatial resolution using empirical retrieval algorithms. These algorithms are XWAVE and XMOD-2 specifically developed for X-Band SAR. XWAVE allows for determining the significant wave height not only for long swell waves, but also for short waves with their wave pattern being hardly visible from SAR. The latter is based on the analysis of image spectrum parameters and spectral noise. As well, the possibility of the imaging quality of longer waves visible from SAR being affected by SAR-specific nonlinear imaging effects is narrowed down. Both the wave and wind field are found to exhibit considerable spatial variability, and their relationship is analyzed. The relevance of the findings of this study with respect to wave/ice modeling is discussed.

Stratospheric Ozone Trends and Variability as Seen by SCIAMACHY from 2002 to 2012

A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and wave events drive episodic advances and retreats of the ice edge, with associated variations in sea ice formation types (e.g., pancakes, nilas). This variability becomes imprinted on the winter ice cover, which in turn affects the melt season the following year.

Global tropospheric ozone variations from 2003 to 2011 as seen by SCIAMACHY

Remote sensing Synthetic Aperture Radar (SAR) data from TerraSAR-X and Tandem-X (TS-X and TD-X) satellites have been used for validation and verification of newly developed coastal forecast models in the German Bight of the North Sea. The empirical XWAVE algorithm for estimation of significant wave height from X-band satellite data has been adopted for coastal application. All available TS-X images in the German Bight collocated with measurements of 6 buoys since 2013 were processed and analysed (53 passages with 196 StripMap images). One TS-X overflight covers strips with length of ~200km and width of 30km over the German Bight from East-Frisian Islands to the Danish coast with a sequence of 3-6 StripMap images. The comparisons with results of wave prediction model show a number of local variations due to variety in bathymetry and wind fronts. The developed Sea State Processor SSP includes XWAVE, pre-filtering of ships and other artefacts and checking results was implemented for NRT services. The comparison with in-situ buoy measurements results in Scatter Index of 20% and RMSE of 0.25m.